Fix port in curl invocation in example.

[jswrenn]

The example server binds port 8080:

tide/src/lib.rs

Line 36 in 46bf28a

//! app.listen("127.0.0.1:8080").await?;

...but the example curl invocations post to port 8000:

tide/src/lib.rs

Lines 47 to 51 in 46bf28a

	//! $ curl localhost:8000/orders/shoes -d '{ "name": "Chashu", "legs": 4 }'
	//! Hello, Chashu! I've put in an order for 4 shoes
	//!
	//! $ curl localhost:8000/orders/shoes -d '{ "name": "Mary Millipede", "legs": 750 }'
	//! number too large to fit in target type

This patch modifies the curl invocations to post to port 8080, instead.

[yoshuawuyts]

Oh, great catch -- thanks so much!